This invention relates to a pumping unit for extracorporeal haematic circulation, in particular in artificial kidneys.
In extracorporeal haematic circulation in artificial kidneys, use is notably made of pumps of the peristaltic type, driven by an electric motor, which draw the blood from a point on the circulatory system (artery) and feed it, after it has been purified in the artificial kidney, into another point (vein).
These pumps are constructed in such a manner that if for any reason the electric motor should fail (for example by an interruption in the electricity supply), it is always possible to manually operate the pump by using a driving handle supplied with it. This is to ensure the continuity of the extracorporeal circulation, avoid the danger of formation of blood coagula, and obtain maximum recovery of the blood in circulation.
Known pumping units place limits on the improved utilisation of the dialyser in which, as is known, the blood yields up its impurities to the dialysis liquid through a semipermeable separation membrane. The dialyser operates in accordance with diffusion and osmosis laws and hence the passage of impurities through the semipermeable membrane depends both on the concentration gradient existing between the blood and dialysis liquid and on the pressure to which the blood is subjected with respect to the pressure of the dialysis liquid. With known pumping units it is not possible to adjust the blood pressure to the characteristics of the dialyser, also because various types of dialyser are commercially available because of which the danger of breaking the dialyser exists. Known pumping units also present disadvantages when, in haemodialysis, the technique is used of connecting an internal arterio-venous fistula to the extracorporeal circuit by means of a single needle.
Moreover the known pumping units have some drawbacks when it is necessary to add the blood with pharmaceutical products, or to provide preventing devices e.g. the so called "dripper device" adapted to shut off air formations.